In a classical signal generator, a baseband signal is generated and modulated. A cyclic prefix is then generated from a last part of the signal and added to the beginning of the signal. The resulting signal is passed through channel emulation means, which for example fade the signal and add noise. The resulting signal is the measuring signal, which is supplied to a device under test. Performing the signal generation by the above-described method though requires a great deal of processing power.
Recently, signal generators for multi-carrier signals have been proposed that include the application of static or fading channel models to the signal prior to signal modulation. Since the creation of a cyclic prefix though is a nonlinear operation, the resulting signal is different from a signal generated by the above-described classical signal generator. Since the channel affects the signal only before cyclic prefix insertion, the cyclic prefix, which is added to the beginning of each symbol, exactly corresponds to the end of the symbol. From a receiver perspective, this difference manifests in the autocorrelation properties of the received signal. The signal received from the signal generator will have ideal autocorrelation properties with distinct correlation peaks separated by symbol length plus cyclic prefix length. In comparison, a signal received from a classical signal generator will have degraded autocorrelation peaks that are shifted in time.
For example the US patent application US 2010/0118818 A1 shows a communication system using cyclic prefixes.
Accordingly, an object of the invention is to create a signal generator and a signal generation method capable of generating a measuring signal including a cyclic prefix which require a low computational power and at the same time achieve a measuring signal with auto correlation properties which are comparable to those of a measuring signal generated by a classical signal generator.